Lecture 01: First Line of Defense: Immune System Basics [Quiz 1]
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Questions and Answers

Which of the following is NOT considered a component of the first line of defence?

  • Chemical secretions
  • Mucous membranes
  • Skin barriers
  • B cells and T cells (correct)

What is the primary role of lysozymes found in saliva?

  • To neutralize acids in the mouth
  • To encourage bacterial growth
  • To cleave glycosidic bonds in peptidoglycan (correct)
  • To strengthen the bacterial cell wall

Which of the following best describes the innate immunity?

  • Rapid and nonspecific defence mechanism (correct)
  • Takes time to develop immunity
  • Slow and specific response to pathogens
  • Long-lasting and adaptive

Which function is NOT attributed to antimicrobial peptides (AMPs)?

<p>Enhancing bacterial reproductive rates (A)</p> Signup and view all the answers

What property of the skin contributes to its effectiveness as a barrier against pathogens?

<p>Slightly acidic pH (D)</p> Signup and view all the answers

What characteristic of normal microflora contributes to the first line of defence?

<p>Compete with pathogens for resources (D)</p> Signup and view all the answers

What is the role of the coughing and sneezing reflexes in the immune system?

<p>Expulsing pathogens from the body (A)</p> Signup and view all the answers

What distinguishes acquired immunity from innate immunity?

<p>It is highly specific and adaptive (A)</p> Signup and view all the answers

What effect does the outer layer of dead keratinocytes have on pathogens?

<p>Provides a barrier against pathogens (A)</p> Signup and view all the answers

Which type of cell is specifically targeted by antimicrobial peptides due to their membrane structure?

<p>Gram-negative bacteria (A)</p> Signup and view all the answers

Flashcards

Skin

The outermost layer of skin, composed of dead cells called keratinocytes, which form a barrier against pathogens.

Mucous Membranes

Mucous membranes line cavities and passages exposed to the environment, such as the nose, throat, and intestines, trapping and removing pathogens.

Innate Immunity

Innate immunity is the body's first line of defense, providing a rapid and nonspecific response to pathogens.

Acquired Immunity

Acquired immunity is a specific and long-lasting response to pathogens, involving lymphocytes like B cells and T cells.

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Specialized Immune Cells

Macrophages, NK cells, and dendritic cells are specialized immune cells that recognize and destroy pathogens.

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Lysozymes

Lysozymes are enzymes found in saliva that break down the cell walls of bacteria, weakening them and making them susceptible to osmotic pressure.

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Antimicrobial Peptides (AMPs)

Antimicrobial peptides (AMPs) are small proteins produced by the body that kill or inhibit the growth of bacteria, viruses, and fungi.

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Psoriasin

Psoriasin is an antimicrobial peptide produced by keratinocytes that targets and inhibits the growth of Gram-negative bacteria.

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Skin pH

The pH of skin is slightly acidic, making it an unfavorable environment for most microbes to thrive.

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Skin Shedding

Shedding of skin cells removes microbes that have adhered to the surface, providing a continuous barrier against infection.

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Study Notes

First Line of Defense

  • Physical Barriers:

    • Skin: A multi-layered barrier, the outer layer composed of dead keratinocytes, effectively blocking pathogen entry. The dermis contains immune cells. The slightly acidic pH, high NaCl concentration, and dryness contribute to its microbial resistance. Constant shedding of the outer skin layers removes potential pathogens.

    • Epithelial linings: Protective barriers lining the nose, throat, and intestines. Mucus and cilia trap and remove pathogens. Coughing, sneezing, and vomiting expel pathogens.

    • Normal microflora: Beneficial microorganisms compete with pathogens for resources, preventing colonization.

  • Chemical Barriers:

    • pH: High acidity in the stomach and low pH on the skin limit pathogen survival.

    • Saliva, tears, and other secretions: Contain antimicrobial substances such as:

      • Lysozymes: Enzymes that break down bacterial cell walls. They cleave the peptidoglycan, weakening the cell wall and causing bacterial lysis due to osmotic pressure.

      • Antimicrobial peptides (AMPs): Short peptides with a wide range of antimicrobial activity. Mechanisms include membrane disruption and sequestration of essential nutrients like zinc.

  • Examples include psoriasin, defensins, and lactoferricin.

  • Defensins: Positively charged peptides (alpha and beta types) that create pores in bacterial membranes, leading to cell death. Lactoferricin chelates iron, making it unavailable to pathogens.

  • Psoriasin targets Gram-negative bacteria, demonstrating selectivity.

Innate Immunity

  • Rapid and nonspecific response: This immediate immune response involves various cells, including macrophages, natural killer (NK) cells, and dendritic cells.

Acquired Immunity

  • Slow, long-lasting, and highly specific response: Involves lymphocytes (B cells and T cells).

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Description

Explore the essential physical and chemical barriers that form the first line of defense in the immune system. This quiz covers the roles of skin, epithelial linings, normal microflora, and antimicrobial substances in protecting against pathogens. Test your knowledge on how these factors contribute to our overall immunity.

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